A Novel Layered Neodymium Squarate MOF Intercalating Free Ammonium and Squarate Ions {(NH4)2[Nd2(H2O)10(C4O4)3]C4O4}n: Synthesis, Crystal Structure and Thermal Decomposition

Abstract

The X-ray study of the title compound {(NH4)2[Nd2(H2O)10(C4O4)3]C4O4}n(1) reveals that it crystallizes in the monoclinic system, space group P21/c (N°: 14), with unit cell parameters, a = 7.483(3), b = 27.866(7), c = 6.766(2) A and β = 103.95(3)°. The crystal structure consists of a Nd–MOF/salt alternating layers, where neodymium–metal organic framework (Nd–MOF) layer lies in (200) plane, formed by isolated [NdO9] polyhedra linked by bridging squarate ligands in µ2- and µ4-coordination modes. The salt layers lie at x = 0 and are sandwiched between Nd–MOF layers; they consist of squarate anions and ammonium cations (in 1:2 ratio). Hydrogen bonds and π–π stacking play a pivotal role in structure cohesion between Nd–MOF layers leading to the formation of a 3D networks. The features of the IR spectrum are consistent with the crystal structure. The TG-DTA reveals that first water is lost from the coordination compound, and then the anionic ligands along with ammonium cations are removed leaving metal oxide as residue of the substance.